IGA LEWIN

University of Silesia,
Faculty of Biology and Environmental Protection, Department of Hydrobiology;
Bankowa 9, 40-007 Katowice
e-mail: iga.lewin@us.edu.pl

Description popularizing the research project

It is hard to be indifferent and pass by a tiny shell lying on the Baltic beach. You simply have to pick it up, shake off the sand and put it into your pocket where there are other tiny white shells. They rattle in your pocket as they are too small to produce the sound of waves like the huge shells of the distant seas. You can really hear the waves in them. Certainly there is a scientific explanation to that sound coming from a spiral shell. But why to bother if we can just free our imagination and finish the story told by the shell ourselves. The shell itself just has to be colorful, as big as it is possible and from far, far away.
Shells of snails do not evoke any romantic associations, rather culinary ones. They are quite big, but nobody tries putting them to ears. They would not sound? They are not linked with adventures? Maybe they are really too small and simply colorless? So what about swan mussels? They are huge, much bigger than an average ear where you could put it. In fact they grow up to 20 cm in length. Would we hear waves in them? Maybe, if we could find them. Swan mussels, swollen river mussels, Lister's river snail, great pond snails and 31 other mollusc species would have a lot to tell us, but there are fewer and fewer places where we can find them. They do tolerate only clean water of rivers with unregulated banks. There are such rivers. One of them is the Wkra river with its tributaries. It is where the species mentioned in the Polish Red Data Book of Animals (Invertebrates) live. They live but they are endangered species. Their presence is meaningful as well. It says that the river is still a river. Hydrobiologists even do not have to put the shell to their ears, they already know everything. And surely they would not be indifferent seeing the huge flat shell on the ground.

Abstract

The objectives of the present survey were to carry out a zoocenological study of the mollusc communities in the lowland rivers under the impact of agriculture, to determine the relationship between the mollusc communities and environmental factors, and to estimate usefulness of the mollusc communities as a factor of water quality.
The Wkra River (249.1 km) and its tributaries: the Łydynia River, the Sona River, the Mławka River, the Raciążnica River, the Szkotówka River, the Naruszewka River and the oxbow lakes have been investigated. The study has been carried out since 2004 to date. The Wkra River starts from Lake Kownatki and connects with the Narew River near Pomiechówek. The Valley of the Wkra River near Pomiechówek constitutes an area protected by the Natura 2000 network (The Natura 2000 is an ecological network in the territory of the European Union).
The samples of molluscs were taken by means of quantitative methods. The analyses of the physical and chemical parameters of the water as well as bottom sediments in terms of organic matter content and granulometry were carried out. The macrophyte species and surface velocity were determined at each sampling sites.
The results of the survey showed a very high concentration of phosphates and nitrates in the tributaries of the Wkra River, in the lower course of the Wkra River and in the oxbow lakes. In total, 35 mollusc species were found. Both Bithynia tentaculata and Sphaerium corneum were eudominant in the Wkra River and its tributaries. The Unionidae were observed mainly in the lower course of the Wkra River. Despite the high concentration of biogenic elements in the water, some species which are legally protected in Poland were observed: Unio crassus, Anodonta cygnea and Sphaerium rivicola. According to the Polish Red Data Book of Animals (Invertebrates) some of mollusc species, i.e.: Unio crassus, Anodonta cygnea and Lithoglyphus naticoides have become endangered (EN) due to the water pollution, the eutrophication of rivers and the habitat degradation. The mollusc communities in the Wkra River are influenced mainly by substratum and nitrate concentration in the water. Because of the amount of biological material which is investigated, some of the analyses, e.g. bottom sediments, statistical analyses (PCA, DCA, Cluster Analysis) have not been completed yet.